The, present invention relates to novel scyphostatin analogues which stand out for acting as inhibitors of SMase so that they are therapeutically useful in connection with a number of diseases, such as an HIV infection, neurodegenerative diseases, inflammatory diseases, ischemia, myocardial infarction, apoplexy, or in the case of atherosclerosis.
Sphingomyelin (N-acyl-spingosyl-phosphoryl-choline, SM) is an integral constituent of both biological membranes and plasma lipoproteins and an important source of forming messenger substances (xe2x80x9csecond messengerxe2x80x9d) such as ceramide which is released following stimulation by enzymes (xe2x80x9csphingoxnyetin pathwayxe2x80x9d), This signal transmission by membrane sphingolipids has been studied intensively in the last few years. SM is metabolized by isoforms of an enzyme similar to phospholipase C, which is referred as sphingomyelinase (SMase). To date, five isotypes of SMase are known. Most mammalian cells are capable of transmitting signals through the SM pathway, the signal transmission being activated by both receptors such as tumor necrosis factor (TNF) receptors or interleukin-1 receptors, and stress, such as U.V. light, oxidants or radiation. The formation of ceramide is nowadays considered co-decisive for the introduction of vital cell processes, such as cell proliferation and apoptosis. This correlation between ceramide formation and apoptosis induction comprises an activation of respectively particular SMase isoforms which display their optimum pH in an acidic (acidic SMases; acid SMases, aSMases) and/or in a neutral environment (neutral SMases; nSMases).
Apoptosis, programmed cell death, proceeds in an irreversible sequence of morphological and biochemical changes. It is the most important regulative mechanism for eliminating no longer required cells during embryonic development and growth or irreparably damaged cells. Various noxious substances, such as TNF/NGF, heat shock, cytostatic agents, ionizing radiation, infections caused by viruses or bacteria, deprivation of various growth factors and cell membrane-permeable ceramides induce apoptosis in different cell types Ceramide as a xe2x80x9csecond messengerxe2x80x9d is involved in programmed cell death in widely differing tissues. For example, it is involved in regulating signal transduction, which eventually results in apoptosis.
The ceramide-induced cell death might play a role in widely differing diseases, such as sepsis, atherosclerosis, neurodegenerative diseases, such as Alzheimer""s disease, Parkinsons"" disease, and infections caused by retroviruses, such as the HIV virus, ceramide-mediated apoptosis having to be assumed in each case.
An infection with the HIV virus, type 1 (HIV-1) together with changes in the cellular metabolism results in a loss of subpopulations of T-lymphocytes, in particular the CD4+ helper cells. There is more and more evidence for the fact that the intracellular redox system, i.e. the equilibnrium between oxidants and antioxidants, HIV infection and lymphocyte-associated ceramide are correlated via the activation of the SM pathway. The ceramide signal system is also involved in the HIV infection when either the HIV expression is regulated or apoptosis is induced. It was possible to show that ceramide initiates the signal cascade resulting in the apoptosis of lymphocytes in HIV-infected patients. This is considered one of the main causes of T-lymphocyte reduction, which ultimately leads to the fully manifested clinical picture. This takes place by induction of apoptosis"" by means of the CD95/APO-1/Fas-receptor/ligand system which activates aSMase and results in the ceramide production. If this is inhibited by treatment with L-carnitine, ceramide synthesis is prevented both in vitro and in vivo. In the final analysis, it seems that the state of the redox systems and the progress of ceramic metabolism permit predictions as to the, intensity of the infection.
Apoptosis also plays a major role in neuronal cell death. It is assumed that there is a direct connection between oxidative stress and the occurrence of neurodegenerative diseases. Cell death in neurodegenerative diseases which can be caused by oxidative stress can be traced back to intracellular signals for SMase activation and the resulting ceramide production, Oxidative stress is attributed a major role in triggering Parkinson""s disease and Alzheimer""s disease, for example. Although the mechanisms inducing these diseases are not yet fully clear, the affected brain centers of the diseased persons have an increased apoptosis rate which is presumably due to an increased ceramide concentration.
SM/ceramide is also involved in chronic or acute inflammatory diseases. Both sepsis and the consequences of septic shock as-well as multiorgan failure have developed into the main cause of death in critical care units. Based on clinical, experimental and epidermologic data, sepsis is nowadays considered an inflammatory response to infections showing signs of severe defective organic functions herein, TNFxcex1 is the central mediator for the development of septic shock. Septic patients have increased serum TNFxcex1 concentrations and also cell-associated ceramide concentrations. It was possible to show that there is a direct connection between ceramide and TNFxcex1 concentrations. Since TNFxcex1 causes intracellular ceramide formation, the inflammatory response falsely modulated by TNFxcex1 might be blocked in spite of increased TNFxcex1 concentrations in the plasma by adding, SMase inhibitors, which would reduce the ceramide formation. Observations, of similar quality were also made in the case of other cellular reactions triggering sepsis. It would be possible to control the apopotosis rate and thus treat septic patients by interfering with the sphingolipid metaoblism to thus control and/or reduce the ceramide production.
Finally, SM metabolites and SMase also play are role in atherogenesis. The (phospho)lipid-protein complex xe2x80x9clow density lipoproteinxe2x80x9d (LDL) is important for phospolipids and neutral lipids in the plasma and very susceptible to oxidative and enzymatic modification. The oxidative or enzymatic modification of LDL comprises a number of chemical and biophysical changes of the lipoprotein. The resulting modified LDL (mLDL) is considered the biologically relevant proatherogenic lipoprotein which contains an abundance of active components. Cellular defective regulations or the injury of endothelial cells by activation of the cellular suicide mechanism resulting in apoptosis are regarded as the key steps for the development of atherosclerotic plaques. It was found that mLDL plays a double role in the case of artherosclerosis: low doses of mLDL are involved in the proliferation and synthesis of the extracellular matrix of the smooth muscle cells (SMC) during the early stage of atherosclerosis. In the advanced stage, when there is sufficient mLDL in the plaque, it may induce apoptosis in the SMC.
This results in instability and ruptures of the plaques and thus in the clinical consequences of artherosclerosis. mLDL induces the proliferation and apoptosis of SMC, Although many mechanisms are unclear, ceramide appears to act as an effector of a cellular response caused by mmLDL. mmLDL is an oxidation product of LDL (mmLDL, minimally modified LDL). Following internalization and lysosomal degradation, mmLDL containing as such a considerable SM proportion, supplies a substrate for the ceramide formation and stimulates the SM/ceramide pathway. The reduction of the aSMase activity offers a possibility of modulating the mLDL-rnediated cell death.
The modulation of endogenous ceramide generation) above all the reduction thereof, is thus a central aspect for the development of new (preventive) therapeutic approaches. This can be effected by inhibiting the membrane-bound neutral sphingomylinase (N-Smase), for example. A natural inhibitor of sphingomylinase is known. It is scyphostatin (FIG. 1) which could be isolated from Trichopeziza mollissima in 1997 for the first time1,2. However, this inhibitor can hardly be used in medicine thus far since it is chemically and metabolically very unstable. Furthermore, there was no possibility of synthetically obtaining this inhibitor or analogues thereof.
Thus, the invention is substantially based on the technical problem of providing novel scyphostatin analogues which do not show the drawbacks of the naturally occurring scyphostatin, i.e. can be produced synthetically and display increased chemical and metabolic stability.
This technical problem is solved by providing the embodiments characterized in the claims.
For the first time, the present invention comprises the chemical synthesis of biologically active analogues of scyphostatin. The active substance can be optimized by varying the described stages. For example, the substitution of the fatty acid amide side chains is possible compared with the fermentation method. The authentic natural substance has a polyene as a substituent (trienoyl fragment) at a corresponding position. Said derivatives are sensitive to oxidation according to the present state of knowledge. The natural substance is also unstable in acid, which is not the case for the compounds according to the invention (intermediate stages and end compounds).
It was found surprisingly that when the below described scyphostatin analogues according to the invention are used, the drawbacks of the naturally occurring scyphostatin are avoided, i.e. due to a structure simpler than that of the natural compound they have above all an increased chemical and metabolic stability. Therefore, they are predominantly suited for treating diseases having an inflammatory component such as sepsis, diseases of the rheumatic form, atherosclerosis as well as neurodegenerative diseases and potentially apoptosis-mediated diseases such as Alzheimer""s disease, Parkinson""s disease, ischemia, apoplexy, myocardial infarction and AIDS.
Thus, the present invention relates to a compound of formula 
in which
R1, R2, R3, R5 and R6, which may be equal or different, represent a hydrogen atom, an OH group, an SH group, an O-alkyl, O-aryl, O-acyl, sulfonic acid, thioalkyl, thiophenyl, alkyl, alkenyl, alkinyl, aryl or acyl residue or a halogen; atom, and
R4 is a fatty acid residue, a C6-C20 alkyl, alkenyl, alkinyl or aryl group, this compound being also characterized in that it can inhibit sphingomylinase (Smase) or
a pharmaceutically compatible salt thereof.
In the present invention, the term xe2x80x9calkyl residuexe2x80x9d for residues R1, R2, R3, R5 and R6 is an unbranched or branched C1-C12 alkyl chain, comprising the methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec.-butyl, tert.-butyl, n-pentyl, isopentyl, neopentyl, tert.-pentyl, 2-methylbutyl, n-hexyl, isohexyl, 2-methylpentyl, 2,3-dimethylbutyl, n-heptyl, 2-methylhexyl, 2,2-dimethylpentyl, 3,3-dirnethylpentyl, 3-ethylpentyl, n-octyl, 2,2-dimethylhexyl, 3,3-dimethylhexyl and 3-methyl-3-ethylpentyl group, for exaiple. Short alkyl chains, such as methyl, ethyl or propyl are preferred. However, cycloalkyl residues having 3 to 12 carbon atoms are also suited. Examples thereof are the cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, or cyclodecyl groups. Cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl are preferred. The same applies correspondingly to the xe2x80x9cO-alkylxe2x80x9d or xe2x80x9cthioalkylxe2x80x9d group.
As to the residue R4 the alkyl group has six to twenty C atoms. Here, groups are preferred which have more than 8 C atoms, such as the n-octyl group, n-nonyl group, n-decyl group, 3-methyl-3-ethylhexyl group, n-undecyl group, n-dodecyl group and cyclic alkyl residues, such as cyclooctyl, cyclononyl or cyclodecyl groups.
In the present invention, the term xe2x80x9calkenyl residuexe2x80x9d for residues R1, R2, R3, R5 and R6 stands for unbranched or branched C2-20 alkenyl residues. Examples thereof are vinyl, propenyl, isopropenyl, allyl, 2-methylallyl, butenyl or isobutenyl, hexenyl or isohexenyl, heptenyl or isoheptenyl, octenyl or isooctenyl groups. Vinyl, propenyl and isopropenyl are preferred. Cycloalkenyl residues having 4 to 30 carbon atoms are also suited, Examples thereof are cyclobutenyl, cyclopentenyl or cyclohexenyl, cycloheptenyl, cyclooctenyl, cyclononenyl or cyclodecenyl groups. Cyclobutenyl, cyclopentenyl or cyclohexenyl are preferred.
As to residue R4 the alkenyl group contains six to twenty C atoms. Alkenyl groups are preferred which have more than 8 C atoms, which may be linear, branched or cyclic. The same applies analogously to the alkinyl group. Polycyclic alkyl or alkenyl residues comprise norbornane, adamantane or berizvalene.
R1, R2, R3, R4, R5 and R6 can also be selected from any monocyclic or polycyclic C6-20 aryl residues. Examples thereof are a carbocyclic, monocyclic residue, e.g. the phenyl group, a heterocyclic, monocyclic residue, e.g. the groups thienyl, furyl, pyranyl, pyrrolyl, imidazolyl, pyrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyrazinyl, thiazolyl, oxazolyl, furazannyl, pyrrolinyl, imidazolinyl, pyrazolinyl, thiazolinyl, triazolyl, tetazolyl as well as the positional isomer of the hetero atom or atoms which may comprise these groups, a residue consisting of carbocyclic condensed rings, e.g. the naphthyl group or phenanthrenyl groups, a residue consisting of condensed heterocyclic rings, e.g. benzofuranyl, benzothienyl, benzimidazolyl, benzothiazolyl. The aryl residues may be unsubstituted or substituted. Suitable substituents are e.g.:
C1-C4 alkyl, such as methyl, ethyl, propyl, etc.
substituted alkyl residues, such as trifluoromethyl, trifluorobutyl, pentafluoropropyl, pentafluorobutyl, pentafluoropentyl, heptafluorobutyl, or nonafluorobutyl group or 2-chloroethyl,
acyloxy, such as acetoxy or a residue of formula:
xe2x80x94Oxe2x80x94COxe2x80x94(CH2)nCH2H, wherein n=1 to 5, 
alkoxy, such as methoxy, ethoxy, propytoxy, isopropyloxy, butyloxy,
alkylthio, such as methylthio, ethylthio, propylthio, isopropylthio, butylthio,
carbamoyl,
alkenyl, such as vinyl, propenyl,
alkinyl, such as ethinyl, propinyl, and
hydroxy
carboxy
halogen, such as fluorine, chlorine, bromine, iodine
CONH2,
CONH-alkyl
CON(alkyl)2 
nitro
amino
C1-C4 alkylamino.
In the present invention, the term xe2x80x9cacyl residuexe2x80x9d stands for acetyl, propionyl, butyryl or benzoyl, for example. Correspondingly, the acyl residue can also be available as an O-acyl residue.
In the present invention, the term xe2x80x9cfatty acid residuexe2x80x9d stands for an aliphatic, saturated carboxylic acid having an almost exclusively unbranched carbon chain. The fatty acid residue preferably contains 6-30 C atoms, the fatty acid residue is preferably CO(CH2)14CH3.
The term xe2x80x9chalogen atomxe2x80x9d stands for fluorine, chlorine, bromine or iodine atom, chlorine and bromine being preferred.
In a preferred embodiment of the compound according to the invention, the sulfonic acid residue is OSO2CH3.
In another preferred embodiment of the compound according to the invention, R1, R2, R3, R5 and R6 are a hydrogen atom each.
A compound according to the invention in which R4 is CO(CH2)14CH3 is even more preferred, the compound hexadecanoic acid-[1-hydroxymethyl-2-(1-hydroxy-2-oxo-cyclohex-3-enyl)ethyl]amide (13) being most preferred.
The term xe2x80x9cpharmaceutically compatible saltxe2x80x9d comprises the salts of inorganic acids, such as hydrochloride, hydrobromide, sulfate, perchlorate, nitrate and phosphate, as well as the salts of organic acids, e.g. acetate, oxalate, tartrate, citrate, succinate, maleate and fumarate.
The compounds according to the invention can be produced using the method described in below Examples 1 to 3. Their therapeutic suitability, i.e. the inhibition of the membrane-bound neutral sphingomylinase (SMase) or the influence of the intracellular ceramide concentration can be determined by known methods; see e.g.1,2,8,9. 
The present invention also relates to pharmaceutical preparations which contain a pharmacologically active amount of a compound according to the invention together with a pharmaceutically compatible carrier. Suitable carriers and the formulation of such pharmaceutical preparations are known to the person skilled in the art. Suitable carriers comprise e.g. phosphate-buffered common salt solutions, water, emulsions, e.g. oil/water emulsions, wetting agents, sterile solutions, etc. The pharmaceutical preparation according to the invention can be available in the form of an injection solution, tablet, ointment, suspension, emulsions a suppository, etc. It can also be administered in the form of depots (microcapsules, zinc salts, liposomes, etc.). The kind of administration of the pharmaceutical preparation depends inter alia on the form in which the active substance is available, it may be oral or parenteral. The methods of parenteral administration comprise the topical, intra-arterial, intramuscular, intramedullary, intrathekal, intraventricular, intravenous, intraperitoneal, transdermal or transmucosal (nasal, vaginal, rectal, sublingual) administration. The administration can also be made by microinjection. The suitable dose is determined by the attending physician and depends on various factors, e.g. on the patient""s age, sex and weight, the kind and stage of the disease, e.g. AIDS, the kind of administration, etc.
Finally, the present invention also relates to the use of a compound according to the invention for treating a disease which is correlated with an increased ceramide concentration or in which a reduction of the ceramide concentration is desirable. This is preferably sepsis, a disease of the rheumatic form, atherosclerosis, a neurodegenerative disease such as Alzheimer""s or Parkinson""s disease, ischemia, apoplexy, myocardial infarction or AIDS. The antiapoptotic activity of the compounds according to the invention is shown in FIG. 3.